Harley-Davidson Model W: Harley's First Flathead
Harley-Davidson's first flathead didn't have a V-twin engine. The Model W, also known as the Sport or Sport Twin, used a 584cc opposed twin with one cylinder pointing toward the front wheel and the other toward the rear. Built for the 1919–1923 model years, it had a low center of gravity, an external flywheel and a transmission built into the engine cases.
Harley has never had much trouble finding riders loyal enough to tattoo the company name on themselves. Getting someone to buy their first motorcycle has been another problem. Long before the Buell Blast, Harley tried to reach those buyers with a motorcycle that looked almost nothing like its big V-twins.
Why Harley built a flat twin
The Sport Twin was intended to be light, easy to handle and comfortable to ride. Harley also wanted a machine that would keep more of its oil on the inside. An exposed, lubricated chain could throw oil onto the motorcycle and the rider's clothes, while separate engine and transmission assemblies provided plenty of places for leaks.
The British Douglas already used an opposed twin with its cylinders arranged fore and aft. Harley adopted that general layout for the Model W. Instead of sticking out to either side like the cylinders on a BMW boxer, the Sport's cylinders followed the frame. The engine sat low between the wheels, keeping the motorcycle narrow and putting its weight close to the ground. The opposed pistons also gave it smoother running than Harley's familiar F-head V-twins.
Harley promoted the Sport to European buyers and women as well as new riders at home. Women were already making long motorcycle trips; Addie and Gussie Van Buren had crossed the country in 1916. The Sport gave Harley a smaller machine to advertise to that audience. Entertainer Gertrude Hoffmann appeared in Sport advertising, and rider Lillian Hauerwas wrote about her machine in The Harley-Davidson Enthusiast.
A flat twin and a flathead
The two terms describe different parts of the engine. Flat twin refers to the opposed cylinders. Flathead refers to the side-valve arrangement, with the intake and exhaust valves beside the cylinder rather than in an overhead-valve cylinder head. An engine can be a flat twin without being a flathead, and a flathead doesn't have to be a flat twin.
The Model W was Harley-Davidson's first production side-valve engine. It was not the first flathead motorcycle made by any manufacturer, and it was not the 45-cubic-inch V-twin that Harley introduced a decade later. The Model W displaced 35.64 cubic inches, or 584cc, from a 2¾-inch bore and 3-inch stroke. Factory literature advertised a little over six horsepower.
| Model years | 1919–1923 |
|---|---|
| Engine | Air-cooled, fore-and-aft opposed twin; side valves |
| Displacement | 35.64 cubic inches / 584cc |
| Bore × stroke | 2¾ × 3 inches |
| Claimed output | Approximately 6 horsepower |
| Transmission | Three-speed, hand shifted |
| Suspension | Trailing-link front fork; rigid rear frame |
The engine, gearbox and outside flywheel
Look at the left side of a Sport Twin and the large round flywheel is hard to miss. Harley placed it outside the crankcase, where its diameter wasn't limited by the size of the cases. The flywheel helped smooth out the engine's power pulses, while the cylinders remained low in the frame.
The clutch and three-speed transmission were incorporated into the engine assembly, with the gearbox above the crankshaft. Helical gears drove a wet multiplate clutch, eliminating the separate primary chain used on Harley's larger twins. The final drive still used a chain, and an enclosure allowed that chain to run in an oil bath. The long chain case is one of the easiest ways to recognize a Sport in a period photograph.
Putting these components together reduced the number of separate housings and potential oil leaks. It didn't make the motorcycle incapable of leaking, but it was a deliberate effort to make ownership less messy. The engine also had automatic lubrication, with a hand oil pump available when needed.
Each cylinder and its head were made as one casting. There was no separate head to unbolt, but the valves were arranged for access without removing the engine from the frame. The intake and exhaust manifolds were combined in a single casting, with separate passages. Heat from the exhaust warmed the incoming fuel mixture; the intake charge and exhaust gases did not share one open passage.
The engine formed the lower structural member of the frame, a layout known as keystone construction. Up front, the Model W had its own trailing-link fork and coil spring rather than the leading-link arrangement used on other Harleys of the period. The rear wheel was rigidly mounted, with the sprung saddle providing some relief for the rider.
Mountain trails and long-distance runs
The Sport Twin soon had more to its credit than smooth running and clean trousers. In July 1919, Jack Fletcher rode one up Mount San Antonio in California, better known as Old Baldy. The route followed a burro trail to a summit more than 10,000 feet above sea level. Harley publicized the climb as a first for a motor vehicle.
Hap Scherer took a Sport on the Three-Flag run, traveling from the Canadian border through the United States to the Mexican border in 64 hours and 58 minutes. The British Columbia-to-Tijuana route covered more than 1,700 miles. This was a record for small motorcycles, on roads that could include mud, sand and stretches a modern rider would consider a trail.
Accounts of the Sport's endurance work also credit it with a record run between New York and Chicago, along with a contractor's trouble-free 1,200-mile trip through Death Valley while surveying possible hotel and railroad sites.
Scherer's travels continued beyond the Three-Flag run. In 1920, he and his Sport received the first transcontinental tour medal awarded by the Motorcycle and Allied Trades Association, a predecessor of the AMA.
The Model W and the Indian Scout
Indian introduced the Scout for 1920, a year after the Model W arrived. Its 596cc side-valve V-twin was close to the Sport's displacement, but it offered substantially more power. Published figures commonly put the original Scout at about 11 horsepower against the Harley's six.
The Scout had the V-twin layout American buyers already knew, along with a better claim to outright performance. The Sport countered with smooth running, a low seat and easy handling. Both were smaller motorcycles intended for solo use, so a buyer didn't have to be shopping for a large sidecar outfit to compare Harley with Indian.
Why the Sport Twin disappeared
For a motorcycle meant to attract new customers, the Model W was expensive. Early examples cost $335. An electrically equipped Sport cost about $380 in 1920, when a larger 61-cubic-inch Harley was roughly $418. A buyer already spending that much could move up to the big twin for relatively little more.
Then there was the Ford. Cheap new and used Model Ts were taking over the transportation business that motorcycles had once served. A car could carry a family and their luggage, and it offered protection from the weather. In a November 1920 speech to dealers, Walter Davidson blamed Ford's pricing and production volume for taking customers away from motorcycles. The postwar economic downturn made an already difficult sales job worse.
Harley cut the Sport's price to about $275 by its final year. It found a better following in Europe than in the United States, but export sales weren't enough to keep it in production. The Scout's performance, the price of Harley's own bigger twins and competition from inexpensive cars all worked against it.
Before the familiar Harley flatheads
The Sport Twin ended with the 1923 model year, after five model years and almost 10,000 motorcycles.
Harley continued developing side-valve engines, but the later motorcycles used different layouts. Single-cylinder models returned for 1926. The 45-cubic-inch D-series V-twin followed in 1929, and the larger V-series flatheads arrived for 1930. The 45 would go on to power motorcycles such as the Servi-Car and the wartime WLA.
Despite the shared letter, the later WL and WLA engines were not enlarged versions of the Model W Sport Twin. Nor was the Sport the engine that became the overhead-valve Knucklehead in 1936. Harley's first flathead was an earlier, separate design, with its cylinders stretched along the frame and its flywheel outside the crankcase.